The development of driver assistance systems in vehicles such as lane keeping, braking assist, parking assist and adaptive cruise control systems has led to vehicles which can function more or less autonomously.
With the introduction of new driver assistance systems follows requirements that the systems are safe to use and also that the driver of the vehicle feels comfortable in trusting the systems to function satisfactorily.
Steering assistance systems commonly identify the lane boundaries of the road and act to position the vehicle close to the center of the lane to maximize the distance to the lane boundaries. However, it is not always desirable to position the vehicle at the center of the lane. For example, for a multi lane road with meeting traffic it may be desirable to position the vehicle further away from the meeting traffic to increase safety margins.
Moreover, when traveling through a curve the optimum path is typically not the center of the lane. A human driver would often cut the curve both to reduce the driving distance and to maximize the curvature of the vehicle path in order to reduce the centrifugal forces acting on the vehicle and on the driver, thereby increasing the comfort of the driver. Moreover, by maximizing the radius of the travel path through the curve, there is less risk that the vehicle will loose traction. To maximize the radius of curvature of a path through a curve, the vehicle is positioned towards the outer lane boundary when approaching the curve and then moves towards the inner lane boundary in the curve. When approaching the exit of the curve, the vehicle is again positioned closer to the outer lane boundary, thereby passing the curve along a path having a larger radius then a path following the center of the lane.
In US2013/0006473, a method and control unit for determining a cutting trajectory of a curve section of a roadway is described. The method and system aims at providing an automated approach mimicking human behavior. Accordingly, it is suggested to position vehicle to reduce the curvature to minimize lateral acceleration (g-force) on vehicle and vehicle occupants.